The present invention relates to a technique for manufacturing a semiconductor integrated circuit device; and, more particularly, the invention relates to a technique which is effective when applied to the lithography processing used in a semiconductor integrated circuit device manufacturing process.
In the manufacture of a semiconductor integrated circuit device, a lithography technique is used as a method of transferring a fine pattern onto a semiconductor wafer. In such a lithography technique, a projection exposure system is used, and a pattern of a photomask (hereinafter referred to simply as “mask”) attached to the projection exposure system is transferred onto a semiconductor wafer (simply “wafer” hereinafter) to form a device pattern.
A mask pattern of an ordinary mask, which the present inventors have studied, is formed by patterning a light shielding film of chromium (Cr), for example, formed on a transparent quartz substrate. For example, this patterning work for the light shielding film is performed in the following manner. First, an electron beam-sensitive resist is applied onto the light shielding film, and then a desired pattern is plotted to the electron beam-sensitive resist by means of an electron beam plotter, followed by development to form a resist pattern of a desired shape. Subsequently, using the resist pattern as an etching mask, the light shielding film is subjected to patterning by dry or wet etching, followed by removal of the resist pattern and subsequent washing, to form a light shielding pattern of a desired shape on the transparent quartz substrate.
Various mask structures have been proposed in line with the recent tendency toward improvement of the resolution attainable in the lithography process. For example, Japanese Published Unexamined Patent Application No. Hei 4(1992)-136854 discloses a technique using a halftone type phase shift mask as a means for improving the resolution of a single transparent pattern. According to the technique disclosed therein, a surrounding portion relative to a single transparent pattern is made translucent, that is, a light shielding portion of the mask is made translucent, and then, in this state, the phase of a very small amount of light passing through the translucent portion and having a sensitivity not higher than that of a photoresist and the phase of light passing through the transparent pattern are inverted. Since the light which has passed through the translucent film is inverted in phase with respect to the light which has passed through the transparent pattern serving as a main pattern, there occurs a phase inversion at the boundary portion, and the light intensity at the pattern boundary approaches zero. As a result, the ratio between the intensity of the light which has passed through the transparent pattern and that at the pattern boundary becomes relatively large, and so a light intensity distribution is obtained which is higher in contrast in comparison with a technique not using the translucent film. This halftone type phase shift mask corresponds to a mask in which the light shielding mask of the foregoing ordinary mask has been replaced with a halftone phase shift film, and it is fabricated by almost the same process as the ordinary mask manufacturing process referred to above.
Japanese Published Unexamined Patent Application No. Hei 5(1993)-289307 discloses a technique of forming a light shielding film by a resist film with a view toward attaining simplification and high accuracy of the mask manufacturing process. The method disclosed therein utilizes the property that an ordinary electron beam-sensitive resist or a photosensitive resist shields a vacuum ultraviolet light having a wavelength of approximately 200 nm or less. According to this method, it becomes unnecessary to use an etching step for a light shielding film and a resist removing step, thus providing a reduction of the cost, an improvement of the dimensional accuracy, and a decrease in the number of defects.
Japanese Published Unexamined Patent Application No. Sho 55(1980)-22864 discloses a masking technique for lithography using a pattern formed by a laminate of a metallic film and an organic material layer. According to the technique disclosed therein, a photoresist pattern for patterning a chromium layer on a main surface of a glass substrate is irradiated with argon ions and is thereby fixed to the chromium layer pattern, thereby improving the shielding effect against the exposure light.
Japanese Published Unexamined Patent Application No. Sho 60(1985)-85525 discloses a technique in which a photoresist is applied onto a mask having a defect to be remedied, and then a focused, charged particle beam is radiated onto a tiny area of the photoresist, which area is to remedy a defect in the mask, to form an opaque carbon film in that area.
Further, Japanese Published Unexamined Patent Application No. Sho 54(1979)-83377 discloses a technique in which an opaque emulsion is buried into a local defective portion of a photomask to effect the correction of pattern.